How to get 4k (3840 x 2160) resolution with Apple TV 4K (2021)?

• Yes you need a 4K capable HDMI cable.
• You also need content that is 4K. The Apple TV 4K will only display content in the form it is transmitted to the Apple TV, for example it will not take 1080P content and upgrade it to 4K.
• Your TV must be a 4K TV.

1. If i need 4k capable HDMI cable, how do i tell if it is 4k capable? Most of the HDMI-cables came with 4k monitors used in the office or with the Xiaomi Box 4k. Go to Amazon and do a search for a 4K HDMI cable, you will find LOTS of them. For example: Amazon.com: 4K 60HZ HDMI Cable 6.6FT,Highwings 18Gbps High Speed HDMI 2.0 Braided Cord-Supports (4K 60Hz HDR,Video 4K 2160p 1080p 3D HDCP 2.2 ARC-Compatible with Ethernet Monitor PS 4/3 HDTV 4K Fire Netflix : Electronics
2. Is there a good way to check if the video is 4k? when using Youtube app i only get 1080. When watching TV+/Netflix/Viaplay i cant find a way to adjust/control the resolution? Not really a universal method. I am not a Youtube subscriber except for their free stuff when I want to learn how to do something. You will need to ask your question on a Youtube forum. On Netflix it is much easier, subscribe to their 4K package and almost everything is in 4K. On Premium channels like , Disney +, HBO Max etc almost everything is 4K content. If an app is free and it's content is free, apply the rule "You get what you pay for."
3. HDMI 1 and HDMI 2 supports 4K HDCP 2.2. Will that matter for the signal from the Apple TV 4k (2021) That is not as critical at this point so please don't worry about it.

3. HDMI 1 and HDMI 2 supports 4K HDCP 2.2.

Then you will need to connect to one of those. Not HDMI 3 and HDMI 4, which will likely have HDMI 1.4 ports with HDCP 1.x. HDCP-protected 4K content requires HDMI 2.0 ports with HDCP 2.2 (or better).

HDMI cables have a bandwidth rating. For 4K content, it is best to look for 18 Gbps certified cables (or better). That may be printed on the cable, but information there is not a requirement for cables.

On Apple TV video settings, set you HDMI output to YCbCr with Chroma 4:2:0. Chroma 4:4:4 is not really better here, as ALL streaming video is encoded 4:2:0 anyway. It also saves 50% HDMI bandwidth, allowing for other video properties (resolution, Hz, dynamic range) at higher settings.

Okay and good luck.